1. Field of the Invention
The present invention relates to a method and device for making a cylinder block of an engine for an automotive vehicle.
2. Description of the Prior Art
In making a cylinder block of an engine, it has been conventionally known that a plurality of cylinder liners are disposed adjacent to one another and casted together with a light metal, such as an aluminum alloy, to get a desirable sliding property of a cylinder bore against a piston, as disclosed in Japanese Patent Public Disclosure No. 62-77149, laid open to the public on Apr. 9, 1987.
Japanese Patent Public Disclosure No. 61-155645, laid open to the public in 1986, proposes to reduce the length of the cylinder block by bringing the cylinder liners close to one another in a longitudinal direction thereof. A plurality of cylinders are arranged within the cylinder block.
It should, however, be noted that a molten light metal material has difficulty in reaching an end portion of a cavity between the cylinder liners successfully as the distance between the cylinders is reduced. Specifically, if the cylinder liner is formed with a flange portion at the top end thereof for improving a seal property between the cylinder block and a cylinder head, the difficulty is remarkable, because the distance between the cylinder liners is further reduced at the top end thereof, which forms a dead end for the molten material in the cavity. This may result in a casting defect, such as a blow hole. This kind of defective cylinder block may induce a crack therein.
Additionally, since the distance between the cylinder liners in the vicinity of the flange portion thereof is smaller than in other portions, the cooling speed of the molten material around the flange portion is greater than at other portions in terms of heat capacity.
Such differences in the cooling speeds produces a residual internal stress. Consequently, the residual internal stress may induce a crack in the cylinder block.